Notice that many oils are now called "part synthetic", probably because "semi-" implies that it is half synthetic oil and half mineral oil. That is probably not true. I wonder which "part" is synthetic? Or rather, what percentage of the oil is actually synthetic. 35%? 10%? 2%? Are we now talking about a marketing gimmick?

I need much more than 2% of a "feel good" sensation with my oil!

 

At the oil forum previously mentioned, I have seen people go 2-3 years on the same syn oil oci before changing. if you only do 3K miles a year, why not change the oil every other year... I personally change my oil once a year.

 

FWIW, in my view if you use a good oil-major-made fully syn and only do 3 or 4000 a year in reasonably long journeys, every two years is fine. (takes cover). Having said that, the more oil is changed the better.
Greg

 

In my way of reasoning, it does not matter if the oil sits in the
jug or the sump.

If the car has not done an excessive number of miles, I am
comfortable not changing the oil until it gets to the the number
of miles I have decided is reasonable.

Don't even care if it is mineral or synthetic when it comes to time
in the sump or miles used.

On certain makes it has been observed that the vehicles employing
full synthetic according to European standards, were less likely
to encounter sludge and oil screen clogging. This is on certain
makes where this is a known problem due to bad design of the
positive crankcase ventilation system.

 

Is this also valid for standard non synthetic oil or is this more prone to dgradation over time, miles or no miles?

 

See Plums' third paragraph.
greg

 

In my mind yes.

But, being from Belgium you have better access to Euro ACEA A3/B4 rated oils.

In particular, Castrol synthetic made in Belgium and Germany are pretty
good in this category. Also Total/Elf of course, which is found only in little
small shops here. In Belgium, if it is labelled synthetic, it is full synthetic
without question.

If cost is a concern, there is always the alternative of changing the filter
in between full oil changes.

 

On the subject of oil filter/ oil change interval, it's possible to buy an additional oil filter that works in conjunction with normal oil filter but has capability to filter down to microscopic particle size .
Normal oil filter that filter full oil flow are only able to filter down to a particle size of 15 to 40 microns, yet oil film thickness is around 3 microns.

So normal filters leave particles of up-to 40 micron circulating in the filtered oil.
Bypass oil filter can filter down to much smaller particle size of 1 micron and remove over 99% of water from oil.

Benefit should be less engine wear, longer interval between oil change without compromising on engine wear due to oil contamination.